1) Field of the Invention
The present invention relates to an illuminant display device which is used to construct a large-sized display unit which employs LED illuminant elements as its light emitting sources and is installed mainly outdoors.
2) Description of the Related Art
As a large-sized display unit, conventionally, there is known such a display unit as shown in FIG. 1. In such a device an LED illuminant element 100 is sealed by a transparent resin 101 which has a spherical leading end portion and serves as a circular convex lens to thereby form an LED lamp 103 having an electrode lead extending therefrom. A large number of LED lamps 103 are wired to and mounted on a wired substrate 102 and the wired substrate 102 is mounted in a case 104 the front surface of which is opened in a round or square shape so as to form an LED combined lamp device 105. The LED combined lamp devices 105 are arranged vertically and horizontally and are then respectively mounted to a box member 107 to be located on the outer wall of a building, for example, by use of stop members 106 to thereby form a large display screen. The display screen is controllably turned on and off with each of the LED combined lamp devices 105 as one illuminant dot so as to be able to display desired characters, symbols and the like.
However, in the above-mentioned conventional display unit, when a large number of LED combined lamp devices 105 are arranged vertically and horizontally and mounted onto the box member 107, respectively, at least the optical axes of the respective LED combined lamp devices 105 arranged in vertical and horizontal lines must be aligned substantially to a view position, from the viewpoint of visibility. For this reason, as the number of the LED combined lamp devices 105 to be mounted increases, it is more troublesome to coincide the optical axes of the individual LED combined lamp devices 105 arranged in horizontal lines with the view position to when mounting combined lamp devices 105 by use of the stop members 106.
Also, when the display unit is installed onto the wall of a building and the like in consideration of the visibility at the practical view position, the mounting surface of the box member 107 for mounting the respective LED combined lamp devices 105 must be previously machined such that it is inclined at a desired angle so as to be able to obtain a desired angle of view. Or, in order to be able to obtain a desired angle of view when the respective LED combined lamp devices 105 are mounted, various cases 104 having different mounting angles must be prepared. This makes it complicated to machine the box member 107 when the respective LED combined lamp devices 105 must be mounted to the box member 107 in such a manner to be able to obtain a desired angle of view at the practical view position, resulting in installation increased costs.
Further, the above-mentioned conventional display unit is disadvantageous in that, when turning on the lamp bodies to display desired characters, symbols and the like respectively constructed by illuminant dots, a visor portion of the case 104 blocks the incidence of the sunlight into the illuminant dots to enhance the relative illuminous brightnesses of the dots with respect to the external brightness and to improve the display contrast of the dots, while heat generated by the respective LED lamps 103 of the individual LED combined lamp devices 105 disposed on the wired substrate 102 is radiated into the ambient air, with the result that the temperature of the air in the case 104 is caused to rise. The thus elevated hot air is caused to flow in such a way as shown by a one-dot chained line in FIG. 1 due to the existence of the visor portion. That is, the hot air tends to remain within the case 104 and is not so that the case is well ventilated. For this reason, the heat radiation and convection of the case 104 is bindered resulting in elevating the ambient air temperature within the case 104, which in turn raises the temperature of the LED lamps 103. This results in an a degradation of the illuminant properties and in shortening of the life periods of the lamps 103.